The present invention relates to an emulsifiable concentrate for a phytosanitary composition, emulsified in water, intended for spraying onto crops, in particular the leaves and trunks of fruit trees for the purposes of protection, in particular from insects, but also for their fungistatic properties preventing the development of diseases. It also relates to the emulsified phytosanitary composition, its method of production, its use, but also the protective film deposited onto the plants.
It is known to use phytosanitary compositions to improve crop protection, these compositions being capable of fulfilling the role of fungicide or also insecticide. They are generally sprayed onto crops in the form of water/oil emulsions in the presence of surfactant additives.
The use of oils of petroleum origin emulsified in water and sprayed onto crops as an insecticide is long-established. Suitably prepared, such oils are generally less phytotoxic than many synthetic pesticides, and make it possible to target acarids, flies, scale insects, chinch bugs, aphids and other crawling or flying insects while having only a moderate effect on the development of trees, plants and crops in general. However, the type of oil and the type of surfactant additive must be non-toxic to plants. Most of the surfactants used are harmful to the environment and toxic to aquatic organisms. The manufacturer will choose from the conventional refined oils obtained from crude oil and/or distillates originating from refining by solvent extraction or by hydrotreatment of base oils, those which will be the least toxic but most effective for example against insect and/or fungal attack. Thus it has been noted that the higher the paraffin content of the oil produced, i.e. comprising compounds having a linear or branched saturated carbon chain, the more effective it is against insects and the less phytotoxic to plants. However, the pour point of such oils having a high concentration of normal paraffins is higher, making their application more difficult in temperate countries, in particular for treatments carried out in winter, as the concentrate obtained from this oil congeals.
In their final formulation, such water/oil emulsions generally comprise from 1 to 3% by weight of an emulsifier with respect to the quantity of hydrocarbons in order to ensure the stability of the emulsion throughout crop spraying. Conventional emulsifiers include the ethoxylated alkylphenols, but also combinations of additives as described in U.S. Pat. Nos. 6,673,360 and 6,615,031. These patents suggest combining polyethoxylated alcohols comprising C10-C16 carbon chains, the average number of ethoxylated groups per carbon chain being 2.8, in a mixture with glycerol mono/dioleates. They recommend the use of hydrocracked and/or hydroisomerized oils, comprising more than 99% saturated compounds, these combinations of additives making it equally possible to incorporate soft water or hard water, i.e. having a high salt content, into these emulsions.
The purpose of the present invention is to make available emulsifiable concentrates that are stable during storage, easily form an emulsion, but which break on contact with the plant to form the homogenous oil film over the crops, in particular the trunks, branches and leaves, in order to perform an insecticide function, and from which the water is instantly removed by runoff. This dual requirement for stability before and during spraying and immediate separation afterwards is central to the invention. Moreover, the surfactant system must be harmless to the environment. Moreover, a further purpose of the present invention is to obtain stable emulsifiable concentrates that can easily be transported, avoiding unnecessarily transporting quantities of water since it is available on site, and the emulsifying of which is facilitated at the site of the crops to be treated. A further purpose of the invention is that, when the emulsion breaks on contact with the plants and bushes, the quantity of water remaining in the deposited protective film is minimal.
The subject of the present invention is thus an emulsifiable concentrate for an emulsified phytosanitary composition, comprising more than 90% by weight of at least one mixture of hydrocarbons having a distillation cut greater than 250° C., comprising less than 20% by weight n-paraffins and less than 1% aromatics, and from 1 to 4% by weight of a mixture of at least two surfactants TA1 and TA2, such that TA2 is more hydrophobic than TA1, the HLB of the mixture of which varies from 6 to 10. Once sprayed on the trees and the leaves, the emulsified compositions of these concentrates form a film which will act as an insecticide, or also a fungicide: the application of these compositions may thus help to cure diseases or may also protect crops from potential diseases caused by the presence of harmful insects and/or to the occurrence of fungal species which are unfavorable to their development. These concentrates are harmless both to the environment and to humans. Moreover, these compositions deposited as a film do not block photosynthesis by the plants although the film slows their growth. This drawback can advantageously be mitigated by planning the spraying periods according to the desired speed of growth and the detrimental effect of the surrounding environment with respect to crop growth. The film deposit is primarily a physical treatment: the insecticidal effect is obtained by asphyxia of the insects present (lack of air) or as a barrier limiting access.
Within the framework of the present invention, the concentrate (in the form of an emulsion) advantageously comprises from 0.0001% to 1% by weight of water in order to avoid the appearance of a deposit corresponding to precipitation of TA1. Moreover, preferably a mixture of surfactants will be chosen, the HLB difference between TA1 and TA2 of which varies from 3 to 11 and the HLB of the mixture of which is comprised between 6 and 10.
Among the hydrocarbons originating from refining, mixtures are preferred that comprise less than 10 ppm sulphur and less than 100 ppm aromatics, and among these the hydrodewaxed hydrocarbons containing more than 50% by weight isoparaffins and desulphurized and dearomatized hydrocarbons containing more than 20% by weight naphthenes. By naphthenes is also meant di- and tricyclic naphthenes. The advantage of these hydrocarbons is that unlike normal paraffins, their pour point determined by the ASTM D97 is substantially lower than that of the normal paraffins or n-paraffins and can be well below −10° C., which facilitates their transport and their storage in cold environments.
More particularly, the hydrocarbons containing more than 60% isoparaffins originating from isodewaxing processes, having a distillation cut comprised between 300 and 400° C., the pour point of which is below −10° C. are preferred. Among these non-phytotoxic hydrocarbons, hydrocarbon mixtures comprising more than 50% by weight of hydrocarbons containing from 15 to 30 carbon atoms are preferred, and preferably more than 70% of hydrocarbons containing from 18 to 26 carbon atoms. Other hydrocarbons can be used, these are gas oil cuts having boiling points above 250° C., originating from hydrocracking vacuum distillate gas oils or other refining processes, these cuts having been desulphurized and/or dearomatized by catalytic hydrogenation then distilled into cuts with ranges of less than 75° C. The preferred cuts, of temperatures varying from 300 to 400° C., comprising more than 20% naphthenes, have the advantage of achieving pour points below −15° C. The concentrate according to the invention will preferably comprise from 2 to 3% surfactant TA1 and from 0.1 to 0.9% surfactant TA2. In order to obtain the optimum stability of the concentrate, its water content must be maintained between 0.05 and 0.5% by weight of the concentrate.
Among the surfactants available on the market, TA1 is chosen from the carboxylic acids, optionally polyalkoxylated, comprising a carbon chain with from 16 to 20 carbon atoms having at least one olefin bond, each polyalkoxylated group comprising from 3 to 15 alkoxyl radicals, itself comprising 1 to 4 carbons per oxygen atom. The HLB of this surfactant will preferably vary between 5 and 16, and preferably from 8 to 12. In a preferred embodiment of the invention, the surfactant TA1 is a polyethoxylated oleic acid comprising from 4 to 8 ethoxylated radicals, preferably 6 ethoxylated radicals on average. The surfactant TA2 is chosen from sorbitan mono- and/or polycarboxylates, polyethoxylated sorbitan mono- and/or polycarboxylates, glycerol mono and/or polycarboxylates or polyethoxylated sorbitan mono- and/or polycarboxylates, wherein the polycarboxylate groups comprise 1 to 3 carbon chains of 12 to 20 carbon atoms having at least one olefin bond, and each polyethoxylated group comprises 1 to 5 ethoxylated groups. The HLB of the surfactant TA2 varies from 1 to 11 and preferably from 1 to 5. Sorbitan monooleate and glycerol monooleate and their mixture are preferred.
A further subject of the invention is the emulsion comprising from 0.5 to 10% by weight of the concentrate as described above and from 99.5 to 90% fresh and/or salt water. Preferably the mixture is emulsified (or macro-emulsified) such that the size of the oil droplets are not too large to allow a minimum stability of the emulsion for sufficient time for spraying onto the crops, but not too small to allow the emulsion to break on the leaf and for the water to run off. These conditions correspond to creaming time or destabilization time of the emulsion measured in the laboratory by the CIPAC (Collaborative International Pesticides Analytical Council) MT36 method. In order to obtain optimum stability of the emulsion, a creaming time of less than 10 minutes is preferred, preferably comprised between 25 seconds and 2 minutes. Preferably, the emulsion comprises from 0.5 to 3% by weight of the concentrate and from 97 to 99.5% fresh and/or salt water.
A further subject of the invention is the method of preparing the emulsion at the crop treatment site. Once transported to the spraying site, the concentrate will be mixed in a tank with the necessary quantity of water. The resulting mixture will be emulsified by means of a static emulsifier or a rotor-stator mixer placed inside the tank or on a by-pass pipe external to the tank allowing recirculation of the emulsion and its homogenization.
A further subject of the invention is use of the emulsion for insecticidal and/or fungicidal crop treatment in which the crops may be of any kind. The emulsion is particularly suitable for fruit tree growing, in particular banana and citrus fruit growing (orange, lemon trees, etc.). A final subject of the invention is the homogenous oil film deposited on the crops, in particular on the trunks and leaves, comprising less than 5% water, preferably less than 0.5%. The surfactants TA1 and TA2 are entrained with the water.